JPS6253530B2 - - Google Patents

Abstract

Hardener for epoxy resins based on (a) araliphatic or cycloaliphatic diamines with 4 amino hydrogen atoms, which are liquid at ambient temperature, or derivatives thereof with at least 3 amino hydrogen atoms, (b) optionally conventional modifiers for the polyamines according to (a) and (c) optionally conventional additives, containing (d) 0.1 to 10% by weight of primary aliphatic monoamines the alkyl groups of which contain 5 to 18 carbon atoms, and a process for hardening epoxy resins with hardeners of this kind.

Description

[Detailed description of the invention]

The present invention relates to a curing agent for epoxy resins and a method for curing epoxy resins with this curing agent. Although it is known to react epoxide resins with polyamines to produce infusible and insoluble moldings and coatings, conventionally pourable low molecular weight polyepoxide compounds are reacted with equivalent amounts of araliphatic or aliphatic compounds. It has not been possible to obtain transparent, chemical-resistant and water-resistant elastic cured products by reacting with cycloaliphatic polyamines or their modified products at room temperature. Aroaliphatic or cycloaliphatic polyamines or their modified products can be used in combination with liquid low molecular weight polyepoxides to provide short shelf life or pot
gives rise to a reactive mixture of lichen, which cures very slowly when applied in thin layers. Although the resulting coatings exhibit good chemical resistance, they are cloudy, have very poor flow properties and have only low water resistance. The cause of this phenomenon is the absorption of CO ₂ and water from the air, which converts a portion of the amino groups into carbaminates or carbonates and inhibits their reaction with epoxy groups. In order to overcome this drawback, German Patent Application No. 1770832 discloses that polyepoxide compounds are prepared in the presence of alkylphenols and possibly in the presence of customary additives without any concomitant use of solvents. Moldings and coatings are produced, for example by reaction with a cycloaliphatic polyamino compound containing at least two primary and/or secondary amino groups at temperatures below 20°C, A polyepoxide compound, which is liquid at the processing temperature, is reacted with a liquid mixture of a polyamino compound and a liquid alkylphenol, in which the sum of the primary and/or secondary amino groups and the hydroxyl groups of the alkylphenol are combined. Molar ratio (0.9~1.1):
1 is proposed. However, the incorporation of free alkylphenols has a detrimental effect on the chemical resistance of moldings and coatings made from araliphatic or cycloaliphatic polyamines and epoxy resins. In order to overcome these drawbacks, DE 21 64 099 discloses that polyadducts based on amines and 1,2-epoxide compounds having one or more epoxide groups in the molecule have been described. In this method, the amine has the general formula H(NH-R-) _n NH-R'-NH ₂ [where m is 0 to 10 and R and R' may be the same or different from each other, and 2 to 40,
In particular, unbranched or branched alkylenes having 2 to 20 C atoms and optionally containing one or more carboxylic acid amide groups in the alkylene chain. It is the basis. ] The products obtained by cyanalkylation of amines of the formula are used, the cyanalkylated amines containing at least two H atoms bonded to the basic nitrogen atom. Furthermore, according to DE 24 60 305 A1, arylalkylamine-acrylonitrile adducts, such as cyanethylated m- or p-xylylene diamines, are used to produce transparent molded bodies with a glossy surface. Therefore, it can be used together with liquid epoxy resin. Cyanethylated bis-(aminoalkyl)-cyclohexane is mentioned in U.S. Pat. No. 3,478,081 as a curing agent for epoxy resins to give moldings with good flexibility and high thermal stability. . The use of cyanoalkylation products of araliphatic or cycloaliphatic polyamines likewise has a detrimental effect on the chemical resistance of moldings and coatings. A further disadvantage in the case of cyanalkylated products is often undesirably long processing times (pot life). Finally, it contains an amino group attached to a cycloaliphatic residue and that cycloaliphatic residue is attached directly or through a bridging atom to another cycloaliphatic residue. Monoamines, optionally polyvalent aliphatic- or cycloaliphatic amines such as 4,4'-diaminodicyclohexyl, 4,4'-diaminodicyclohexylmethane and 1,2- or 1,4
It is known to prepare epoxy molding or coating compositions in admixture with diaminocyclohexane). The minimum amount of monoamines is 40%. The present inventor has proposed that a molded article (including a flat one such as a coating) which avoids these drawbacks and is nevertheless chemical resistant has 6 to 18 d alkyl groups, especially 6 ~Aliphatic primary monoamines having 10 carbon atoms ~0.1~
When used in combination with 10% by weight, especially 0.5 to 5% by weight (based on the sum of components a and d), a aromatic fat which is liquid at room temperature and has 4 amino hydrogen atoms; group- or cycloaliphatic diamines or derivatives thereof having at least 3 amino hydrogen atoms, b optionally the customary modifiers therefor, and c optionally customary additives. It has been found that this can be obtained by using a curing agent consisting of: An essential feature of the invention is that components a), b and d are mutually compatible. The diamine according to a is preferably m-xylylene diamine or a liquid mixture thereof with p-xylylene diamine, and more preferably, for example, 1,3- or 1,4-bis-(aminomethyl-)cyclohexane or a mixture of these diamines. Suitable derivatives are, for example, Mannitz bases, which are particularly preferred and which can be prepared by condensation of amines with alhydes (for example formaldehyde or acetaldehyde) and phenols (for example phenol, cresol or p-tert-butylphenol). can get. However, this material also partially reacts with the liquid epoxy resin mentioned above,
Amine adducts may be formed which are still liquid and therefore processable. Suitable monoamines a, which are generally liquid, are for example linear or branched hexyl-, -heptyl-, -octyl-, -nonyl-, -decyl- or -dodecylamines, particularly preferably n-octylamine or iso- They are nonylamines, and may be used alone or in a mixed state. According to the method of the invention, a completely transparent material with good chemical resistance, especially towards salts, acids and alkalis and good aging stability, high water resistance and a smooth, scratch-free surface. A composition for casting molding and a molded article (including a coating) are obtained. It is possible to use solvents, diluents and/or plasticizers in total amounts of less than 30% by weight. Processing in a suitable two-component spray gun is likewise possible and has the advantage of extending the limited service life of the reaction mixture. The reaction between the curing agent of the present invention and the epoxy resin takes place rapidly even at temperatures of 0 DEG to 20 DEG C., so that no heating of the reaction mixture is necessary. Suitable epoxy resins are all products or solutions of solid epoxy resins which are liquid at room temperature and contain one or more epoxide groups in the molecule. This includes, in particular, polyphenols (especially bisphenols) or polyhydric alcohols (eg glycerin, pentaerythritol or butanediol-1,4) and epihalogenhydrins (eg epibromohydrin, especially epichlorohydrin). There are liquid low molecular weight polyglycidyl ethers which can customarily be obtained by reaction with hydrins). Also suitable are polyglycidyl esters and liquid polyepoxides obtained from low molecular weight unsaturated hydrocarbons and hydroperoxides. Examples of suitable polyepoxide compounds, advantageously having a molecular weight below 600, include diglycidyl ether of 2,2-bis(p-hydroxyphenyl)-propane and pentaerythritol, glycerin, propylene glycol-1,2 or Butanediol
There are 1,4 polyglycidyl ethers. However, solid epoxy resins can also be used if they become liquid in the solvent. The polyepoxides can be used alone or in admixture with one another or with added secondary amounts of monoepoxide compounds, the amount of which is, for example, up to 5% by weight. These include epoxidized hydrocarbons with at least 4 C-atoms and one unsaturated bond, such as butylene, cyclohexene and styrene oxide, rogen-containing epoxides such as epichlorohydrin, monohydric alcohols such as methyl -, ethyl-, butyl-, 2-
glycidyl ethers of monohydric phenols (e.g. phenols, cresols and other phenols substituted in the o- or p-position), glycidyl ethers of unsaturated carboxylic acids, olefinic unsaturations Epoxidized esters of alcohols or olefinically unsaturated carboxylic acids and acetals of glycidaldehyde are suitable. Customary modifiers b include, for example, softeners and
Special solvents that dissolve the amines a and b and the epoxy resin are suitable. Suitable solvents include, for example, aromatic hydrocarbons such as toluene and xylenes alone or in mixtures with alcohols such as n- and i-butanol and amyl alcohols, also ketones such as methyl ethyl ketone and methyl isobutyl ketone, and also benzyl. There are mono- or diethers of alcohol, ethylene or 1,2-propylene glycol with methanol, ethanol, propanol and various butanols, each alone or in mixtures with each other. Examples of softeners include monohydric alcohols (e.g., n-butanol, amyl alcohol,
(2-ethylhexanol, nonanol, benzyl alcohol, each singly or in a mixture thereof), γ-butyrolactone, δ-valerolactone, ε-caprolactone, furfuryl alcohol, low- and high-molecular weight polyhydric alcohols (such as glycerin, trimethylolethane or - propane, ethylene glycol and oxyethylated - or oxypropylated polyhydric alcohols)
Examples include phthalate esters. The hardeners may additionally contain other customary additives, such as inert fillers, pigments, dyes, soluble dyes, etc. Suitable fillers are, for example, silicon oxide, hydrated aluminum oxide, titanium dioxide, glass fibers, sawdust, mica, graphite, calcium silicate and/or sand, as well as customary pigments with a particle size of, for example, 5 to 500 μm. Finally, the hardener mixture may be admixed with other customary hardeners for reaction with the polyepoxide compounds in amounts of up to 10% by weight, based on the total amount of hardeners. In the examples and tables below, HAV means hydrogen equivalent, TZ means pot life and RT means room temperature. Pre-products for the Examples The following mixtures are prepared: A 136 g of m-xylene diamine (1 mol)
is mixed with 94 g of phenol (1 mol) in a three-necked flask equipped with a stirrer, thermometer and separator and heated to 70°C. Then 58 at 70℃
g of 36.5% concentration formaldehyde (0.7 mol)
for about 4 hours, then add water to a maximum of 4 hours.
Evaporate under reduced pressure at 70 DEG C. and heat the mixture to 90 DEG C. for 1 hour under 40-60 mbar. The reaction product is maintained under these conditions for an additional hour, cooled and vented. The Mannitz base condensate obtained has a viscosity of 2500 mPa.s (25° C.) (HAV70). B 150g m-xylylenediamine (1.3 mol)
is mixed with 94 g of phenol (1 mol) under stirring in the apparatus described under A) and heated to 70°C. Then, at 70° C., 107 g of formaldehyde (36.5% concentration) (1.3 mol) are introduced over the course of 3 hours. After a period of 30 minutes at 70°C, set vacuum and distill off the water. 40~60m of reaction product
Maintain at 105 °C for 30 min under bar, cool and ventilate. The resulting Mannitz base condensate is
9900 mPa.s (25
℃) viscosity (HAV83.7). I: Examples 1 to 5 (curing agent) The following amounts of polyamine and monoamine are stirred at 30° C. under a nitrogen atmosphere until thorough mixing takes place: 1 979 g of m-xylylenediamine and 3g
of octylamine; HAV of mixture = 34.5. 2 97 g m-xylylene diamine and 3 g isononylamine (a mixture of nonylamine isomers containing about 90% 3,5,5-trimethylhexylamine); HAV of the mixture = 34.5. 3 a 97.5 g of Mannitz base condensate A) and 2.5 g of octylamine; HAV of the mixture =
69.8. 3 b 97.5 g of Mannitz base condensate A) and 2.5 g of isononylamine; HAV of the mixture
=70. 3 c 97.5 g of Mannitz base condensate A) and 2.5 g of decylamine; HAV of the mixture =
70.2. 3d 97.5 g of Mannitz base condensate A) and 2.5 g of n-hexylamine;
HAV=69.3. 3 e 99.0 g of Mannitz base condensate A) and 1.0 g of ocdecylamine; HAV of the mixture
=70.3. 4 a 75 g Mannitz base condensate B, 22.5 g
of benzyl alcohol and 2.5 g of octylamine; HAV of mixture = 107. 4 b 75 g Mannitz base condensate B, 22.5 g
of benzyl alcohol and 2.5 g of isononylamine; HAV of the mixture = 107.4. 5 97 g of cyclohexane-1,4-bismethylamine and 3 g of octylamine;
HAV=36. Comparative curing agent V1: m-xylylene diamine (hydrogen equivalent 34), V2: Mannitz base condensate A, V3: 75 g of Mannitz base condensate B and 25 g of benzyl alcohol under nitrogen atmosphere at 30°C. and stir until thorough mixing occurs (HAV of mixture = 111). V4: Cyclohexane-1,4-bismethylamine (HAV=35.5). Examples 6 to 10 (Coatings) Coatings are prepared using the products listed under I and comparative curing agents and epoxy resins as follows and are tested and evaluated in the industrial application. 100 g of low molecular weight diphenylolpropane-diglycidyl ether with a viscosity of about 10000 mPa.s and an epoxide equivalent of 183 are mixed with an amount of the respective curing agent corresponding to the hydrogen equivalent and each of two glass plates A coating film with a thickness of 200 μm is applied on top. One board was stored for 24 hours at 23°C and 40-50% relative humidity, and the other board was stored at 5°C.
Save for 24 hours. These coatings are tested for tack, haze and hardness. These coated boards are then placed in a water bath for 30 minutes and after drying the changes in the coating (turbidity) are evaluated. As can be seen from the table, the coatings produced with the hardeners according to the invention exhibit satisfactory surface properties, whereas in the case of the comparative examples more or less turbidity is observed. Another drawback overcome by the curing agent according to the invention and demonstrating an industrial advance in curing agents is:
It is this turbidity. On the one hand, the formation of carbonates or carbaminates that attract and exceed turbidity impedes interlayer adhesion of other layers applied thereon. On the other hand, the crosslinking density in the cured coating is reduced by carbonate or carbamate formation. Points of attack are created for chemicals such as diluted organic acids, thereby reducing chemical resistance.

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Claims (1)

[Scope of Claims] 1a Aroaliphatic or cycloaliphatic diamines that are liquid at room temperature and have 4 amino hydrogen atoms, or at least 3 amino hydrogen atoms thereof; Curing agents for resins based on derivatives, the curing agents containing from 0.1 to 10% by weight of aliphatic primary monoamines in which the d alkyl group has 6 to 18 carbon atoms; This percentage display is for components a and d.
The above-mentioned curing agent for epoxy resin, characterized in that it is based on the total of. 2. Curing agent according to claim 1, containing customary modifiers for polyamines according to b, a and c customary additives. 3. The curing agent according to claim 1 or 2, wherein monoamine d is added in an amount of 0.5 to 5% by weight. 4. The curing agent according to any one of claims 1 to 3, wherein the aliphatic monoamine has 6 to 10 carbon atoms. 5. The curing agent according to any one of claims 1 to 4, wherein diamine a is m-xylylene diamine. 6. A curing agent according to any one of claims 1 to 5, in which diamine a in the form of Mannitz base is used. 7. The curing agent according to any one of claims 1 to 6, wherein the epoxy resin is in a liquid state. 8. The curing agent according to any one of claims 1 to 7, wherein the epoxy resin has a molecular weight of 600 or less.